Coil assembly and method of making the same

ABSTRACT

A coil assembly and method of making the same comprising an elongated coil form of insulating material, a first coil on the form having a plurality of coaxial turns with selected spacing between adjacent turns, and a second coil having a single turn or less mounted on the coil form in coaxial relation with and spaced between a pair of adjacent turns on the first coil. The second coil includes a pair of integral connector leads at opposite ends of the turn which leads extend outwardly of the coil form from between spaced adjacent turns of the first coil. Integral connector leads of the first and/or second coil support the coils in a mold forming member during and after fabrication of the coil form, which is integrally molded to support the coils in fixed mutual inductive relationship.

United States Patent Inventor [72] JamesE.Krepps,Jr. 2,771,585 11/1956De Long 336/183 X Bloomiugton, lud- 2,899,631 8/1959 Cushmanm. 336/192 X211 Appl. No 821,837 2,910,529 10/1959 Splitt 336/183 x [22] Filed May5,1969 2,937,350 5/1960 Sasaki 336/183 [45] Patented June 29, 19713,169,234 2/1965 Renskersm. 336/208 X [73] Assignee Sarkes Tarzian Inc.3,443,257 5/1969 Mollman 317/101 (CC) Bloomington, 1nd- 3,486,22412/1969 Chaney 317/101 CC Primary Examiner-T. J. Kozma s4 COIL ASSEMBLYAND METHOD or MAKING THE Mme-Mason, Kolehmainfin, Rathburn & y

SAME 9 Claims 10 Drawmg Figs ABSTRACT: A coil assembly and method ofmaking the same U.S.Cl comprising an elongated coil form of insulatingmaterial a 29/626, 336/651 336/183, first coil on the form having aplurality of coaxial turns with 336/ l92,336/2 8 selected spacingbetween adjacent turns, and a second coil [51 1 Int. Cl 1/04, having aingle turn or less mounted on the coil form in coaxial H011 15/02,HOIfH/O2 relation with and spaced between a pair of adjacent turns on 0Search the first coll The econd coll includes a pair of integral con.I98, 208, 192, 65, 205; 317/ 101 CC; 2 nector leads at opposite ends ofthe turn which leads extend 6215;264/272 outwardly of the coil form frombetween spaced adjacent turns of the first coil. Integral connectorleads of the first [56] References C'ted and/or second coil support thecoils in a mold forming UNITED STATES PATENTS member during and afterfabrication of the coil form, which is 1,713,462 5/1929 Blatterman336/183 integrally molded to support the coils in fixed mutual induc-2,729,796 H1956 Hulst 336/183 X tive relationship.

PATENTED JUN29 |97| SHEET 2 OF 2 FIG. 7

FIG. 6

v INVENTOR JAMES E. KREPP5,JR war/( A,

F I 6. I0

Attorneys COIL ASSEMBLY AND METHOD OF MAKING THE SAME The presentinvention relates to a new and improved coil assembly and a method ofmaking the same. More particularly, the coil assembly of the presentinvention is especially adapted for use as an antenna coil, oscillatorcoil, IF transformer, choke, and the like, as commonly used intelevision, FM and other radio and radar equipment.

In VHF and UHF television, radio, and FM equipment, often the inductancevalues of the coils used require only a single turn or less ofrelatively small diameter mounted on an air core coil form. Thedimensional tolerances of the coils and the spacing or placement of theturns in relation to one another is relatively critical and, if closedimensional tolerances are not maintained, the inductances are notusable for their intended purposes.

It is an object of the present invention to provide a new and improvedelectrical coil assembly and method of making the same.

Another object of the present invention is to provide a new and improvedcoil assembly of the character described for use at VHF and UHFfrequencies which may be readily manufactured on a mass productionbasis, at low unit cost, at relatively low reject rate, and 'withuniform electrical characteristics.

Still another object of the present invention is to provide a new andimproved coil assembly which is especially adapted to be mounted on andconnected to a printed circuit board.

Another object of the present invention is to provide a new and improvedcoil assembly including a first winding having a plurality of coaxialturns and a pair of separate coils, each having a single turn or lessand disposed between adjacent turns of the first winding, said separatecoils being adapted to be connected together through a printed circuitboard connection to form a precisely balanced, center tapped windinginductively coupled to the first winding.

The foregoing and other objects and advantages of the present inventionare accomplished in an illustrated embodiment thereof comprising a newand improved coil assembly having an elongated coil form of moldedinsulating material and a first coil thereon having a plurality ofhelical, coaxially aligned turns with selected pitch or spacing betweenadjacent turns of the coil. A second coil having a single tum or less ismounted on the coil form in coaxial relation with and spaced between apair of adjacent turns on the first coil, and the second coil includes apair of integrally formed connector leads at opposite ends extendingoutwardly of the coil form from between spaced adjacent turns of thefirst coil. The coil assembly is especially adapted for mounting on aprinted circuit board and the coil leads are adapted to physicallysupport and secure the coil assembly in place as well as provideelectrical connection with the circuitry on the printed circuit board.

In constructing a coil assembly in accordance with the presentinvention, preformed first and second coils are positioned in a firstcoil form molding member and are self-supported therein by the coilleads. A second molding member is then closed with the first member overthe first and second coils to accurately position and align the coils inplace and provide accurate spacing between the mutually inductive turns.After the mold is closed, a core pin is inserted into the mold andplastic material is introduced into the mold cavity, preferably in aninjection molding process. When the molded coil form hardens or cures,the mold is opened and the finished coil form positively secures theturns of the first and second coils in proper relation with one another.

For a better understanding of the present invention, reference should behad to the following detailed description taken in conjunction with theclaims and drawings in which:

FIG. 1 is a side elevation of a new and improved coil assemblyconstructed in accordance with the features of the present invention;

FIG. 2 is a bottom elevational view looking upwardly in the direction ofthe arrows 2-2 of FIG. 1;

FIG. 3 is a transverse cross-sectional view taken substantially alongline 3-3 ofFlG. 1;

FIG. 4 is a perspective view illustrating the coil assembly mounted on aprinted circuit board;

FIG. 5 is a perspective view similar to FIG. 4 but illustrating theopposite side of the circuit board and the connection between the leadsof the coil assembly and the circuitry of the circuit board;

FIG. 6 and 7 are schematic, electrical circuit diagrams of coilassemblies in accordance with the present invention;

FIG. 8 is a perspective view illustrating a step in the method of makinga coil assembly inductance in accordance with the present invention;

FIG. 9 is a transverse cross-sectional view taken substantially alongline 9-9 of FIG. 8 and illustrating in dotted lines an upper member asit is moved downwardly into a mold closing position; and

FIG. 10 is a transverse cross-sectional view similar to FIG. 9illustrating both members of the mold in a closed position with V a corepin inserted on the coil form as molded therein.

Referring now, more particularly, to the drawings, therein isillustrated a new and improved coil assembly constructed in accordancewith the features of the present invention and illustrated as a whole inFIGS. 1, 2, 4, and 5 and referred to generally by the reference numeral20. The coil assembly 20 includes a hollow, generally cylindrical coilform 22 formed of integrally molded insulating material and providedwith outwardly projecting supporting foot portions 22a at opposite endsthereof.

The coil assembly 20 includes a first winding 24 having a plurality ofhelical, coaxial turns 25, and the winding 24 may serve as the primarywinding of an antenna coil suitable for use in television or FM tuners.The coil 24 is provided with a pair of integrally formed connector leads26 at the opposite ends thereof and the leads 26 project outwardly ofthe longitudinal axis of the coil form 22 in the same general directionand parallel with the mounting foot portions 221: of the coil form. Theconnector leads, as shown in FIG. I, extend outwardly beyond the outerend surfaces of the mounting foot portions 22a.

in addition to the multitum coil 24, the coil assembly 20 also includestwo separate, single-turn loops or coils 28 and 30, each of which is incoaxial alignment with the turns of the coil 24 and is disposed betweena pair of adjacent turns thereof. As best shown in FIGS. 3, 9, and 10,the single-turn coils 28 and 30 each comprise a single circular loop ofwire with a pair of connector leads 29 and 31, respectively, projectingoutwardly from the ends of the loops in a direction generallyperpendicular to the longitudinal axis of the coil form 22 and generallyparallel with the leads 26 of the multiturn winding 24. The single turnsor loops of the coils 28 and 30 are disposed to lie on planes angularlyintersecting the coil form 22 and are spaced between adjacent turns orconvolutions 25 of the multiturn coil winding 24. The single-turn coils28 and 30 preferably are equal in diameter to the turns 25.

In FIG. 3 is illustrated the single-turn winding 28 which comprises asubstantially circular loop of wire and at opposite ends of the loop areintegrally formed the connecting and supporting end leads 29 which arespaced apart and parallel. The leads 29 extend outwardly and generallynormal of the coil form 22 from points spaced between adjacent pairs ofturns or loops 25 of the multitum winding 24, and thus there is nointerference or contact between the coil leads 29 and the helical turns25, even though the single-turn coils 28 and 30 are positioned directlybetween adjacent turns or convolutions 25 of the multitum coil 24.

FIGS. 6 and 7 are schematic diagrams of typical coil assemblies providedin accordance with the present invention. In FIG. 6 a pair ofsingle-turn coils 28 and 30 are provided which are inductively coupledwith a multitum winding 24 on the common coil form 22. The single-turncoils 28 and 30 are interconnected together externally of the coil form22 (for example, on a printed circuit board, (FIGS. 4 and 5) to form atwo-turn primary winding with a center tap for balanced line input and amultitum coil 24 comprises a'secondary winding of the coil assembly.Since the coils 28 and 30 may be precisely identical, as described indetail hereinafter, and the coupling of each coil to the secondary isexactly the same, the center-tapped primary thus formed is exactlybalanced for coupling to a conventional 300 'ohm twin lead antennainput. Also, either one of the coils 28 or 30 may be used separately asthe sole input coil to match a 75 ohm input, if desired.

In FIG. 7, the single-turn coil 28 is the primary winding, and themultitum coil 24 and single-turn coil 30 are secondary windings. Theschematic diagrams shown in FIGS. 6 and 7 indicate typical VHF-UHFcoupling arrangements in which the coil assembly 20 constructed inaccordance with the present invention may be employed.

, Referring to FIG. 8, in fabricating a coil assembly 20 in accordancewith the invention, each separate coil 24, 28, and 30 is formed with itsrespective connecting and supporting leads 26, 29 and 31, as described.The preformed coils are then placed in a free-standing positionsupported on the lower half or drag portion of a coil form mold member32, which is to be used for the injection molding of the coil form 22.As best shown in FIG. 8, the mold member 32 includes an elongated,substantially semicylindrical recess or cavity portion 32a for formingthe main cylindrical, hollow body portion of the coil form 22, and ateach end of the cavity 320 is formed a transverse slot or depression 32bfor molding of the feet portion 22a. The mold member 32 includessemicylindrical recesses 34 at opposite ends of the elongated cavity 32aand slots 32b for supporting opposite ends of a cylindrical central corepin 36 (FIG. inserted into the closed mold for forming the hollow centerbore of the coil form. The semicylindrical recess or cavity 320 isprovided with a plurality of longitudinally spaced, helically shaped,transverse grooves 37 adapted to receive and support the turns orconvolutions 25 of the winding 24 and lower portions of the single turnor loop of the coils 28 and 30 disposed between the turns 25.

coil turns is established. As best shown in FIGS. 9 and 10, when theupper mold member 40 is moved downwardly into mold closed position (FIG.10), the single-turn coils 28 and 30 are compressed radially and thenheld with precise longitudinal spacing between the turns and coils bythe grooves 41 and 37 in the respective mold members 32 and 40.

After the mold members 32 and 40 are closed together, an elongated corepin 36 is inserted coaxially through the central portion of thecylindrical mold cavity formed by the cooperating recesses 32a and 40a,so that the coil form 22 will be hollow to provide an air core for thecoil assembly. The mold cavity is filled with insulating plasticmaterial, preferably in an injecting molding process, and after thematerial sets or hardens the mold is opened and the finished coilassembly is removed.

The diameter of the mold cavities 32a and 40a is substantially equal tothe mean diameters of the coil convolutions 25 The coil leads 26, 29,and 31 support the respective coils 24, 28, and 30 in a free, standingposition on the lower mold member 32 (FIG. 8) with the turn portions ofthe coils seated in the grooves 37 in the cavity 320. To this end, themold member 32 is formed with a plurality of spaced apart, downwardlyextending bores or holes 39 (FIGS. 9 and 10) for receiving therespective coil leads 26, 29, and 31. At the upper ends adjacent thecavity 32a the bores 39 are enlarged as at 390 to form integral bosses40 of molded insulating material for firmly holding the respective leads27, 29, and 31 of the coils in precise outwardly extending parallelalignment generally normal to the main cylindrical body of the coilform. The drilled bores 39 in the mold member 32 are slightly larger indiameter than the respective leads 26, 29, and 31, of the coils so thatthe coils can be easily inserted into a free standing position as shownin FIG. 8, preferably with an automatic feeding device. When the uppersurface of the lower mold member 32 is exposed as shown, with cavities32a and 32b and recesses 39a and bores 39 readily accessible, thepreformed coils 24, 28, and 30 may be rapidly placed in a precisealignment on the mold member with the leads 26, 29, and 31 seated in thealigning bores 39. After the coils 24, 28, and 30 have thus beenpositioned in free standing position on the open mold member 32, a tophalf of the mold or mating portion 40 is moved downwardly against thelower member 32 (as indicated in FIG. 9 by the arrows) to a mold-closedposition, as shown in FIG. 10. The upper mold member 40 has anelongated, substantially semicylindrical cavity 400 therein for formingthe upper portion of the body of the coil form 22 and v a plurality oflongitudinally spaced, helically shaped, transverse grooves 41 areprovided for receiving the upper half portions of the turns 25 of themultitum coil 24 and the upper half portions of the single-turn coils 28and 30. The cavities 32a and 40a cooperate to form the main body of thecoil form 22 and pairs of the respective grooves 37 and 41 cooperate tohold the turns of the coils 24, 28, and 30 in a precisely spacedrelation so that the desired mutual inductance between the and thecircular loops of the single-turn coils 28 and 30 so that when theplastic material sets, the coils are firmly held in place with thedesired coil diameter and spacing or pitch between turns. Each of thesingle-turn coils 28 and 30 and its respective leads 29 and 31 isconstructed with the loop portion of the coil and the leadssubstantially on a common plane, which bisects the longitudinal axis ofthe coil form at an angle approximately equal to the pitch angle orhelix generation angle of the turns 25 on the multiturn winding 24. Theturns 25 of the multitum coil 24 are arranged in helical configurationand the individual single-turn coils 28 and 30 lie in parallel planeswhich are spaced approximately midway between adjacent pairs of theturns 25. Because of this arrangement, there is no interference betweenthe outwardly extending leads 29 and 31 of the single-turn coils 28 and30 and the helical convolutions 25 of the multitum coil 24, as the leadsproject outwardly from the coil from points spaced between pairs ofadjacent coil turns 25 thereon.

The body of the molded coil form 27 maintains accurate coil diameter andturn spacing between the coils of the coil assembly, and, in addition,integrally molded nub portions 42 (FIGS. 1, 4 and 5) are provided tomore firmly hold the adjacent turns or convolutions of the coils in thedesired pitch spacing outwardly of the outer surface of the main body ofthe coil form. The nub portions 42 are formed by recesses 40b (FIGS. 9and 10) provided in the upper mold member 40 and serve to prevent theturns of the coils from expanding in diameter.

VA finished coil assembly 20 appears substantially as shown in FIGS.1,2, and 3, with a plurality of connecting and supporting coil leads 26,29, and 31 projecting downwardly in the same general or common directionas the supporting foot portions 220 at opposite ends of the coil form22. The completed coil assembly is especially adapted, as shown in FIGS.4 and 5, for mounting on and electrical connection with circuitry on aprinted circuit board 44. The circuit board 44 includes a pluraLity ofcircuit forming conducting strips 45, etc., on at least one facethereof, and a plurality of preciselyspaced holes 46 for receiving therespective leads 26, 29 and 31 of the coil assembly 20 mounted thereon.The coil leads provide means for positively keying the coil assembly inplace on the circuit board 44 and the foot portions 22a of the coil formbear against the surface of the circuit board to maintain proper spacingof the coil axis in parallel relation to the circuit board. The coilleads 26, 29, and 31, extend through the holes 46 in the board and aresoldered to various conducting strips 45 thereon to complete theelectrical and mechanical connection of the coil assembly 20 with thecircuit board. The coil leads serve a dual purpose in properly aligninga mechanically supporting the coil assembly 20 on the circuit board. Thecoil leads serve a dual purpose in properly aligning and mechanicallysupporting the coil assembly 20 on the circuit board 44 and inelectrically interconnecting the coils 24, 28, 30, etc., of the coilassembly with the circuitry on the board. As shown in FIG. 5, theadjacent pair of coil leads 29 and 31 of the respective single-turncoils 28 and 30 project through a common conducting strip 47 on theprinted circuit board 44 and are soldered thereto to produce the circuitconfiguration shown schematically in FIG. 6, wherein each of thesingle-turn coils 28 and 30 comprises a portion of a multiturn winding.The soldered connection 47 between the adjacent supporting coil leads 29and 31 of the coils 28 and 30 connects the two coils in series to form asingle winding which is in a mutual inductive relation with the turns 25of the multitum coil 24. However, the above-described method of assemblyof, the coils 28 and 30 is considerably simpler than an arrangementwherein two multitum coils must be threaded into one another before theyare supported in the bottom mold member. Furthermore, use of thesoldered connection 47 as a center tap provides a precisely balancedinput for coupling to 300-ohm antenna input circuits, as describedheretofore.

While but a single embodiment of the present invention has been herespecifically disclosed, it will be apparent that many variations may bemade therein, all within the scope and spirit of the invention.

What I claim as new and desired to be secured by Letters Patent of theUnited States is:

l. A coil assembly comprising an elongated coil form having a body ofmolded insulating material, a first coil molded in place on said coilform having a plurality of turns with a selected spacing betweenadjacent turns, a second coil having a single turn-or less molded inplace on said coil form in coaxial relation with and spaced between apair of adjacent turns of said first coil, said second coil including apair of integral connector leads at opposite ends of said single turnextending outwardly of said coil from between spaced adjacent turns ofsaid first coil, and insulating support means integrally molded on saidcoil form body around said connector leads for securing said second coilin spaced apart relation between said adjacent turns of said first coil,said connector leads projecting outwardly beyond said support means formaking external electrical connections.

2. The coil assembly of claim 1 including a third coil having a singleturn or less mounted on said coil form in coaxial relation with andspaced between a pair of adjacent turns of said first coil, said thirdcoil including a pair of integral connector leads at opposite ends ofsaid single turn extending outwardly of said coil form between spacedadjacent turns of said first coil, and connector means remote from saidcoil form for interconnecting adjacent connector leads from second andthird coils whereby said coils form a tapped common winding of saidinductance.

.3. The coil assembly of claim 1 in combination with a printed circuitboard having circuit conductors thereon connected with said connectorleads for supporting said inductance on said circuit board, said supportmeans having end surfaces in spacing contact against said circuit board.

4. The coil assembly of claim 2 wherein said connector means comprises aprinted circuit board having circuit eon- 6 ductors thereon, said coilconnector leads extending generally in a common direction toward saidcircuit board and connected to 'said' conductors thereon for supportingsaid inductance on said circuit board, said support means including endsurfaces for contact against said circuit board to maintain a selectedspacing between said board and said coil form body.

5. The coil assembly of claim 1 wherein said connector leads of saidsecond coil are parallel and said single turn or less and said connectorleads lie in a common plane angularly intersecting the longitudinal axisof said coil form.

6. A coil assembly comprising an elongated coil form having a body ofmolded insulating material, a first coil molded in place on said formincluding a plurality of turns with a selected pitch distance betweenadjacent turns, a second coil having a single loop and molded in placeon said coil form spaced between a pair of adjacent turns of said firstcoil, said second coil having a pair of end leads extending outwardly ofsaid form from between adjacent turns of said first coil, insulatingsupport means integrally molded on said form body around said leads forholding said second coil in said spaced apart relation between adjacentturns of said first coil, a third coil having a single loop and moldedin place on said coil form spaced between a pair of adjacent turns ofsaid first coil and including a pair of end leads extending outwardly ofsaid form from between adjacent turns of said first coil, insultingsupport means integrally molded on said form body around the end leadsof said third coil for holding said third coil in spaced apart relationbetween adjacent turns of said first coil, said end leads of said secondand third coils extending, respectively, outwardly of said support meansfor making external electrical connections.

7. A method of making a coil assembly comprising the steps of forming afirst coil with a plurality of coaxial, spaced turns and a pair ofparallel connector leads at opposite ends extending outwardly of thecoiling axis of said turns, forming a second coil having a single turnor less and a pair of parallel connector leads extending outwardly fromthe ends of said turn, placing said first coil on a mold forming memberwith said leads in a coil supporting upstanding position thereon,placing said second coil on said mold forming member with said leads ina coil supporting upstanding position and said single turn in coaxialalignment spaced between a pair of turns in said first coil, and moldinga coil form in said member for holding said first and second coils infixed position relative to each other.

8. The method of claim 7 wherein coaxial alignment between the turns ofsaid first and second coils is obtained by moving a second mold formingmember into a closed position forming a cavity for said coil form.

9. The method of claim 8 wherein said turns are compressed radiallyinwardly during coaxial alignment by moving said second mold formingmember into said closed position.

1. A coil assembly comprising an elongated coil form having a body ofmolded insulating material, a first coil molded in place oN said coilform having a plurality of turns with a selected spacing betweenadjacent turns, a second coil having a single turn or less molded inplace on said coil form in coaxial relation with and spaced between apair of adjacent turns of said first coil, said second coil including apair of integral connector leads at opposite ends of said single turnextending outwardly of said coil form between spaced adjacent turns ofsaid first coil, and insulating support means integrally molded on saidcoil form body around said connector leads for securing said second coilin spaced apart relation between said adjacent turns of said first coil,said connector leads projecting outwardly beyond said support means formaking external electrical connections.
 2. The coil assembly of claim 1including a third coil having a single turn or less mounted on said coilform in coaxial relation with and spaced between a pair of adjacentturns of said first coil, said third coil including a pair of integralconnector leads at opposite ends of said single turn extending outwardlyof said coil form between spaced adjacent turns of said first coil, andconnector means remote from said coil form for interconnecting adjacentconnector leads from said second and third coils whereby said coils forma tapped common winding of said inductance.
 3. The coil assembly ofclaim 1 in combination with a printed circuit board having circuitconductors thereon connected with said connector leads for supportingsaid inductance on said circuit board, said support means having endsurfaces in spacing contact against said circuit board.
 4. The coilassembly of claim 2 wherein said connector means comprises a printedcircuit board having circuit conductors thereon, said coil connectorleads extending generally in a common direction toward said circuitboard and connected to said conductors thereon for supporting saidinductance on said circuit board, said support means including endsurfaces for contact against said circuit board to maintain a selectedspacing between said board and said coil form body.
 5. The coil assemblyof claim 1 wherein said connector leads of said second coil are paralleland said single turn or less and said connector leads lie in a commonplane angularly intersecting the longitudinal axis of said coil form. 6.A coil assembly comprising an elongated coil form having a body ofmolded insulating material, a first coil molded in place on said formincluding a plurality of turns with a selected pitch distance betweenadjacent turns, a second coil having a single loop and molded in placeon said coil form spaced between a pair of adjacent turns of said firstcoil, said second coil having a pair of end leads extending outwardly ofsaid form from between adjacent turns of said first coil, insulatingsupport means integrally molded on said form body around said leads forholding said second coil in said spaced apart relation between adjacentturns of said first coil, a third coil having a single loop and moldedin place on said coil form spaced between a pair of adjacent turns ofsaid first coil and including a pair of end leads extending outwardly ofsaid form from between adjacent turns of said first coil, insulatingsupport means integrally molded on said form body around the end leadsof said third coil for holding said third coil in spaced apart relationbetween adjacent turns of said first coil, said end leads of said secondand third coils extending, respectively, outwardly of said support meansfor making external electrical connections.
 7. A method of making a coilassembly comprising the steps of forming a first coil with a pluralityof coaxial, spaced turns and a pair of parallel connector leads atopposite ends extending outwardly of the coiling axis of said turns,forming a second coil having a single turn or less and a pair ofparallel connector leads extending outwardly from the ends of said turn,placing said first coil on a mold forming member with said leadS in acoil supporting upstanding position thereon, placing said second coil onsaid mold forming member with said leads in a coil supporting upstandingposition and said single turn in coaxial alignment spaced between a pairof turns in said first coil, and molding a coil form in said member forholding said first and second coils in fixed position relative to eachother.
 8. The method of claim 7 wherein coaxial alignment between theturns of said first and second coils is obtained by moving a second moldforming member into a closed position forming a cavity for said coilform.
 9. The method of claim 8 wherein said turns are compressedradially inwardly during coaxial alignment by moving said second moldforming member into said closed position.